Natural gas is commonly considered to consist of methane, but the gas produced from a well normally contains higher hydrocarbons such as propane and butane. Those hydrocarbons are in gaseous form when the gas is collected from the well, but because of their higher boiling points are more readily condensed to liquids. It is desirable to remove higher hydrocarbons from the methane before the natural gas is introduced into high pressure pipelines to prevent condensate from forming in the pipeline and in associated equipment during transport. Those hydrocarbons also have economic value to the well owner or operator.
Approaches known in the prior art for removing higher hydrocarbons from methane at the wellhead include expansion of the produced gas, and the use of refrigerant, to cool the gas and condense some of the higher hydrocarbons. Although these approaches do result in removal of some of the higher hydrocarbons from the predominantly methane stream, their effectiveness is limited because of limitations of the temperature drop that can be achieved.
There remains a need for an efficient and effective process and apparatus for removing hydrocarbons such as propane and butane from a natural gas stream at the wellhead.